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bsnmplib (3)

>> bsnmplib (3) ( FreeBSD man: Библиотечные вызовы )

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NAME



snmp_value_free

 
snmp_value_parse

 
snmp_value_copy

 
snmp_pdu_free

 
snmp_code snmp_pdu_decode

 
snmp_code snmp_pdu_encode

 
snmp_pdu_dump

 
TRUTH_MK

 
TRUTH_GET

 
TRUTH_OK

 - SNMP decoding and encoding library

LIBRARY

Begemot SNMP library
(libbsnmp, -lbsnmp)

SYNOPSIS

#include <bsnmp/asn1.h>
#include <bsnmp/snmp.h>
void snmp_value_free (struct snmp_value *value);
int snmp_value_parse (const char *buf enum snmp_syntax union snmp_values *value);
int snmp_value_copy (struct snmp_value *to const struct snmp_value *from);
void snmp_pdu_free (struct snmp_pdu *value);
enum snmp_code snmp_pdu_decode (struct asn_buf *buf struct snmp_pdu *pdu int32_t *ip);
enum snmp_code snmp_pdu_encode (struct snmp_pdu *pdu struct asn_buf *buf);
void snmp_pdu_dump (const struct snmp_pdu *pdu);
int TRUTH_MK (F);
int TRUTH_GET (T);
int TRUTH_OK (T);

DESCRIPTION

The SNMP library contains routines to handle SNMP version 1 and 2 PDUs. There are two basic structures used throughout the library:

struct snmp_value {
        struct asn_oid          var;
        enum snmp_syntax        syntax;
        union snmp_values {
          int32_t               integer;/* also integer32 */
          struct {
            u_int               len;
            u_char              *octets;
          }                     octetstring;
          struct asn_oid        oid;
          u_char                ipaddress[4];
          uint32_t              uint32; /* also gauge32, counter32,
                                           unsigned32, timeticks */
          uint64_t              counter64;
        }                       v;
};

This structure represents one variable binding from an SNMP PDU. The field Fa var is the ASN.1 of the variable that is bound. Fa syntax contains either the syntax code of the value or an exception code for SNMPv2 and may be one of:

enum snmp_syntax {
        SNMP_SYNTAX_NULL        = 0,
        SNMP_SYNTAX_INTEGER,    /* == INTEGER32 */
        SNMP_SYNTAX_OCTETSTRING,
        SNMP_SYNTAX_OID,
        SNMP_SYNTAX_IPADDRESS,
        SNMP_SYNTAX_COUNTER,
        SNMP_SYNTAX_GAUGE,      /* == UNSIGNED32 */
        SNMP_SYNTAX_TIMETICKS,

        /* v2 additions */
        SNMP_SYNTAX_COUNTER64,
        /* exceptions */
        SNMP_SYNTAX_NOSUCHOBJECT,
        SNMP_SYNTAX_NOSUCHINSTANCE,
        SNMP_SYNTAX_ENDOFMIBVIEW,
};

The field Fa v holds the actual value depending on Fa syntax . Note, that if Fa syntax is SNMP_SYNTAX_OCTETSTRING and Fa v.octetstring.len is not zero, Fa v.octetstring.octets points to a string allocated by malloc(3).

#define SNMP_COMMUNITY_MAXLEN   128
#define SNMP_MAX_BINDINGS       100

struct snmp_pdu {
        char            community[SNMP_COMMUNITY_MAXLEN + 1];
        enum snmp_version version;
        u_int           type;

        /* trap only */
        struct asn_oid  enterprise;
        u_char          agent_addr[4];
        int32_t         generic_trap;
        int32_t         specific_trap;
        u_int32_t       time_stamp;

        /* others */
        int32_t         request_id;
        int32_t         error_status;
        int32_t         error_index;

        /* fixes for encoding */
        u_char          *outer_ptr;
        u_char          *pdu_ptr;
        u_char          *vars_ptr;

        struct snmp_value bindings[SNMP_MAX_BINDINGS];
        u_int           nbindings;
};

This structure contains a decoded SNMP PDU. Fa version is one of

enum snmp_version {
        SNMP_Verr = 0,
        SNMP_V1 = 1,
        SNMP_V2c,
};

and Fa type is the type of the PDU.

The function snmp_value_free ();
is used to free all the dynamic allocated contents of an SNMP value. It does not free the structure pointed to by Fa value itself.

The function snmp_value_parse ();
parses the ASCII representation of an SNMP value into its binary form. This function is mainly used by the configuration file reader of bsnmpd(1).

The function snmp_value_copy ();
makes a deep copy of the value pointed to by Fa from to the structure pointed to by Fa to . It assumes that Fa to is uninitialized and will overwrite its previous contents. It does not itself allocate the structure pointed to by Fa to .

The function snmp_pdu_free ();
frees all the dynamically allocated components of the PDU. It does not itself free the structure pointed to by Fa pdu .

The function snmp_pdu_decode ();
decodes the PDU pointed to by Fa buf and stores the result into Fa pdu . If an error occurs in a variable binding the (1 based) index of this binding is stored in the variable pointed to by Fa ip .

The function snmp_pdu_encode ();
encodes the PDU Fa pdu into the an octetstring in buffer Fa buf .

The function snmp_pdu_dump ();
dumps the PDU in a human readable form by calling snmp_printf (.);

The function TRUTH_MK ();
takes a C truth value (zero or non-zero) and makes an SNMP truth value (2 or 1). The function TRUTH_GET ();
takes an SNMP truth value and makes a C truth value (0 or 1). The function TRUTH_OK ();
checks, whether its argument is a legal SNMP truth value.

DIAGNOSTICS

When an error occurs in any of the function the function pointed to by the global pointer

extern void (*snmp_error)(const char *, ...);

with a printf(3) style format string. There is a default error handler in the library that prints a message starting with `SNMP:' followed by the error message to standard error.

The function pointed to by

extern void (*snmp_printf)(const char *, ...);

is called by the snmp_pdu_dump ();
function. The default handler is printf(3).

ERRORS

snmp_pdu_decode ();
will return one of the following return codes:

Bq Er SNMP_CODE_OK: Success.
Bq Er SNMP_CODE_FAILED: The ASN.1 coding was wrong.
Bq Er SNMP_CODE_BADLEN: A variable binding value had a wrong length field.
Bq Er SNMP_CODE_OORANGE: A variable binding value was out of the allowed range.
Bq Er SNMP_CODE_BADVERS: The PDU is of an unsupported version.
Bq Er SNMP_CODE_BADENQ: There was an ASN.1 value with an unsupported tag.